The present invention relates to a powder beam etching machine for etching a workpiece (hereinafter referred to as a work) by injecting gas containing fine particles into the work.
FIG. 3 shows an example of an arrangement of a conventional powder beam etching machine. A substrate mounting table 22 used as a work mounting table fixed in a cylindrical etching chamber 21 by a support member (not shown) is provided in the etching chamber 21 which is substantially hermetically sealed. A nozzle 24 is provided through a center of an upper wall 21a of the etching chamber 21 with a lower end of the nozzle 24 facing an upper surface of the substrate 23. An opening 21b is formed in the upper wall 21a for feeding and removing the substrate 23. Furthermore, a suction port 26 is provided in a bottom portion of the etching chamber 21 for collecting fine particles.
In the thus constructed power beam etching machine, an etching process is effected on a surface of the substrate by the fine particles injected together with air onto the substrate 23 from the nozzle 24.
However, in the conventional powder beam etching machine shown in FIG. 3, the fine particles which have been injected onto the substrate 23 would flow horizontally after collision, and would then collide with an inner circumferential surface of the etching chamber 21 so that part of the particles would ultimately fly upwardly. As a result, the conventional machine suffers from a problem that a large amount of fine particles would adhere to the inner circumferential surface of the etching chamber 21 and inner surfaces of the upper wall 21a and an upper lid 25 and a stagnation of the fine particles 27 would be formed at corner portions of the etching chamber 21. For this reason, during the etching operation, the fine particles would leak from gaps between the upper lid 25 and the upper wall 21a, and the fine particles would leak to the outside when the upper lid 25 is opened or closed.
The above-noted defects might be overcome by firmly fastening the upper lid 25 onto the upper wall 21a with some sealant. However, in this case, it is necessary to loosen or fasten screws every time substrates 23 are replaced which deteriorates working property. Also, when compressed air is sprayed onto the substrate 23 for cleaning it after the completion of the etching process, the fine particles 27 adhered or accumulated onto the etching chamber 21 would scatter again by the flow of the compressed air. As a result, it would be practically impossible to clean the substrate within the etching chamber. As a result, a discrete cleaning chamber has been conventionally provided in addition to the etching chamber. The substrate 23 which has been worked is conveyed to the cleaning chamber by using a delivery means such as a robotic arm. Then, both sides of the substrate 23 are cleaned in the cleaning chamber. As a result, various mechanisms such as a conveyor mechanism using arms, a compressed air spraying mechanism within the cleaning chamber, add an air discharging mechanisms would be needed to enlarge the system thereby increasing total cost.
On the other hand, in the case where the etching processes are to be carried out by changing kinds of fine particles, when a different kind of particles which has been used in a previous process are left in the etching chamber, different kinds of particles are mixed together to adversely affect the etching process.